Do a barrel roll! ...not again!

[engraverwilliam]

All of a sudden my nice stable ship seems to be trying desperately to do a barrel roll while on it's way up. Not drastically like a mis-placed fuel line but enough that I have to keep my hands constantly on the E and Q keys until I hit orbit.

Any ideas?

[Xarian]

I have the same problem with nearly every ship that I build. Same problem with a slight yaw+roll to the left with my planes. Best guess is that it's a clipping problem that happens when you use the various symmetry options.

[SuperWeegee4000]

That's an aileron roll.

But in all seriousness, aeronautics isn't the most finely honed aspect of the game, and planes are tough to build.

[ASnogarD]

Its a bit hard to give advice based on the little information you supplied...

Assuming its a Rocket and not a Spaceplane , do you have winglets ? ASAS on ? Is it balanced (COM in the middle when viewed from the top down) ? A fuel tank didnt pop off and is balanced on top of another tank (causing fuel weight inbalances)?

Sometimes Struts can cause a lot of spins, especially if you strut the small / med grey tanks used to avoid the overheating when mainsails are attached directly to orange tanks... stutting those smaller tanks to each other can cause spin.

Cross strutting can cause spin if it makes parts of the craft too rigid compared to the main body of the craft.

Some say if your struts touch each other it can cause illogical issues with the physics engine which can manifest as spin (not personally tested this).

[engraverwilliam]

hmm thanks for the ideas to test... perhaps I will upload my craft later for outside testing.

[allmappedout]

Some say if your struts touch each other it can cause illogical issues with the physics engine which can manifest as spin (...)

...All we know, is he's called the Stig.

On a serious note, I have found that asparagus designs have the most significant roll issues, but it does seem to manifest itself in a number of designs.

[MmPMSFmM]

How hard can rocket science be anyway? Let me tell you: It's hard.

[Endeavour]

I think it might have to do with the fact that multiple gimballed engines don't seem to control roll at all. I always assume that six mailsails should be able to stop my spinning, but they don't affect the roll.

[Deejay2000]

How hard can rocket science be anyway? Let me tell you: It's hard.

Kerbal rocket science = (rocket science - science) + explosions

Sometimes for me, it needs more struts.

And other times, it needs more struts.

But if it doesn't need more struts, it needs more struts.

Oh, did I mention that it may need more struts?

Search around your rocket and make sure everything is balanced.

SAS?

STRUTS?

Edited July 17, 2013 by Deejay2000

[spikeyhat09]

to clarify, was your plane doing an actual "barrel roll", or the often neglected but more accurate "aileron roll"?

[MockKnizzle]

It's been my experience with asparagus-styled rockets that the boosters, when under power, can develop a slight twist around the central core that results in the rocket tending to spin. You can correct with control surfaces, but once you cancel out your spin in one direction the boosters will just twist in the other, potentially resulting in the situation you're describing. I've found that a pair of struts at the top and bottom of each booster is plenty to add the rigidity that you need and stop any twisting.

[The Deep Space Kraken]

Lock gimbal on the outer engines. Engine gimbal is usually what causes spinning on asparagus staged rockets.

[Coneshot]

I find that if i have angled fuel lines i get spin, I try to keep them straight and balance with struts...lots of struts..

[theflyingfish]

Don't listen to anyone above. Uncommanded roll in any KSP craft is usually caused by structural flexing due to improper strutting or bugs. The common roll often seen with asparagus staging is because the parallel stages are flexing back and forth, causing the thrust vector to change, causing roll. Every rocket with parallel stages will roll a small amount, regardless of struts. The problem is, because KSP's gimbal algorithms only calculate pitch and yaw, most rockets that rely on engine gimbal for control have dramatically less roll authority, too little to counteract the roll caused be flex.Almost every single KSP aircraft rolls slowly to the left. This is caused by a bug in KSP that makes the left part of a symmetrical group have lower connection strength, making that part bend more, because in KSP, connection stiffness is proportional to connection strength. It is more apparent in large, heavy aircraft, where the structural flexing is more pronounced. To reduce the roll, strut your wings more to reduce flex.

[FITorion]

MOAR SAS

Seriously though if it's spinning you need more things that can apply torque to correct the spin. SAS is that.

[Vanamonde]

If you have a joystick installed, make sure that it is centered.

[Skorpychan]

MOAR SAS

http://i.imgur.com/aP4z0XI.jpg

Seriously though if it's spinning you need more things that can apply torque to correct the spin. SAS is that.

Doing that helps?

[Motokid600]

I second sas modules on top if each liquid booster. It's make or break for some of my craft.

[FITorion]

Doing that helps?

Indeed it does.

[Sof]

Indeed it does.

completely unnecessary if you design your rockets properly though.

I use essentially the same first stage but have no problems with rolling. That SAS would just add weight.

[dave4002000]

Some say if your struts touch each other it can cause illogical issues with the physics engine which can manifest as spin (not personally tested this).

...All we know, is he's called the Stig.

I'm glad i'm not the only one that heard Clarkson's voice when i read that comment...hahahaha

As long as everything is strutted properly, i usually find that a set of winglets in quad symmetry attached at 0,90,180,270 degrees will control all roll moments, during ascent, on anything but the heaviest of rockets.

[bsalis]

Uncommanded roll in any KSP craft is usually caused by structural flexing due to improper strutting or bugs.

That.

Personally I just roll with it.

It seems to me that it's only MechJeb that has the issues with it.

[samstarman5]

It is quite possible the spin is induced by the issues that Squad is currently working on to resolve with .21. I am anxious to see if that is true. SAS has been needing a workover for quite some time.

[engraverwilliam]

I fixed my issue. I have clustered engines. Had to run a strut from the tank to each engine. problemo solved.

[arq]

Yup, radially mounted or clustered engines often get twisted ever so slightly to one side under load, which causes the rocket to spin. Moar struts is typically the solution.